Test results China-balls vs. CeramicSpeed-balls

25. december 2006

Since September 2006 we have been testing different steel balls and 3 types of ceramic balls. 6 balls, 3.50 mm diameter, (the same diameter as are used in our external bottom bracket bearing), shaft speed 4.000 RPM, contact stress 3.6 Gpa The average lifetime for steel balls was 43 hours.

Our ceramic balls did more than 600 hours - 14 times longer lifetime. However the 2 different balls we have tested from China lasted less than 10 hours before serious surface failures. Both types of China ball are used in bicycle applications. Of course 4.000 RPM are a bit more than any bicycle BB will do.

It's not sure that the Chinese ceramic balls will become surface failures like the ones you see on the pictures below. But when the surfaces on the ceramic balls are so rough as shown on the pictures below (before testing), the ceramic balls will grind the steel raceways - really fast indeed.

Next time somebody talks about ceramic bearings - remember that there is a huge difference on the ceramic material itself. Ceramic balls are not just ceramic balls.